Heat exchanger for cooling interior of housing

ABSTRACT

The air inside a housing containing heat generating parts is forced by an inside air fan to flow in a heat exchanger case through an inside air inlet, flow partially upward and partially downward in an inside air passage while being cooled by inner fins, between the inner fins, installed in the inside air passage, that form a heat exchanger heat sink, and discharge from the inside air passage through an upper, first inside air outlet and a lower, second inside air outlet. The air discharged through the two inside air outlets flows over the surfaces of the heat generating parts in the housing, taking heat from them.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger for cooling theinterior of a housing, installable in a small housing and capable ofachieving a high heat exchange efficiency and a high flow rate of insideair.

2. Description of the Related Art

In machining factories and the like, electronic parts and electricwiring parts are often contained and used in a sealed housing to preventthem from being contaminated or damaged by dust, cutting fluid, or thelike. If the electronic parts contained in the housing generate a largeamount of heat and enough heat cannot be dissipated from the surface ofthe housing, the air temperature inside the housing rises and thetemperature of the heat generating parts also rises exceeding theirpermissible limits, resulting in a shorter life, malfunctioning, orother problems of the electronic parts. Since outside air cannot betaken directly into the housing for ventilation to avoid such problems,an alternative method being used is to use a heat exchanger to exchangeheat between the air inside the housing and the air outside the housing.

An example of a prior art heat exchanger for cooling the interior of ahousing by exchanging heat between the air inside the housing and theair outside the housing will be described with reference to FIG. 14.

An inside air passage 19 through which the air inside a housing 2containing heat generating parts flows and an outside air passage 20through which the air outside the housing 2 flows are separated by aheat exchanger heat sink 12 (see FIG. 3) having fins mounted on bothsides of a base plate or corrugated fins 18 (see FIG. 4). An inside airfan 5 forces the air inside the housing 2 to flow in and flow throughthe inside air passage 19. On the other hand, an outside air fan 6forces the air outside the housing 2 to flow in and flow through theoutside air passage 20. With this, heat is exchanged between the airinside the housing 2 and the air outside the housing 2.

Another example of a prior art heat exchanger for cooling the interiorof a housing by exchanging heat between the air inside the housing andthe air outside the housing will be described with reference to FIG. 15.

In this heat exchanger, inner fins 14 and outer fins 16 are thermallyconnected by heat pipes 31 having an extremely high heat conductivity.This heat exchanger has a relatively complicated structure and involvesa higher assembly cost.

Japanese Patent Application Laid-Open No. 2005-150667 discloses a heatexchanger for cooling the interior of a housing, which is a coolingdevice to be retrofitted to the housing and has a double structureformed of an inner air conduit through which the air inside the housingflows and an outer air conduit through which the air outside the housingflows. In this double structure, heat is exchanged between the airinside the housing and the air outside the housing and the heatgenerated inside the housing is thus dissipated to outside the housing.

As a technical trend in recent years, there are demands for downsizingof the housings containing heat generating parts, similarly to otherelectronic devices. Downsizing the housing reduces the amount of heatdissipated from its surface, so it is necessary to increase the amountof heat dissipated by a heat exchanger. Consequently, a small-sized heatexchanger having a high heat exchange efficiency is required. A heatexchanger with a high heat exchange efficiency lowers the temperature ofthe air inside the housing, but does not always lower the temperature ofthe heat generating parts. This is because the amount of heat dissipatedby heat transfer from the heat generating parts to the air inside thehousing is proportional to the difference between the temperature of theheat generating parts and the temperature of the air inside the housing,and is also proportional to the square root of the velocity of the airflowing over the surfaces of the heat generating parts.

The use of a stirring fan is also contemplated to increase the velocityof the air flowing inside the housing, but it requires its installationspace inside the housing and inevitably enlarges the housing. Toincrease the velocity of the air flowing inside the housing withoutusing a stirring fan, it suffices to increase the flow rate of the airflowing through the inside air outlets of the heat exchanger. Toincrease the heat exchange efficiency of a small-sized heat exchanger,heat absorbing fins installed in the inside air passage of the heatexchanger has to be finely pitched to increase their surface areas, butsuch finely pitched fins would cause a significant pressure drop of theair flowing between them and reduce the flow rate as shown in FIG. 13according to the pressure-flow rate characteristics (P-Qcharacteristics) of the inside air fan that forces the air to flowthrough the inside air passage.

As the technique disclosed in Japanese Patent Application Laid-Open No.2005-150667 mentioned above employs a special structure in which asingle motor is used to rotate both the inner air fan and the outer airfan, a plurality of heat exchanger sections, a cooler (heat exchanger)of which case has an irregular structure, and a partition plate having acomplicated shape, parts cost and assembly cost becomes high, and it isdifficult to obtain a high flow rate if a centrifugal fan which caneasily obtain a high static pressure, is used. Even if an axial fan isused, it is usually difficult to obtain a high flow rate because apartition plate is disposed as a shielding obstacle closely facing theinlet or outlet side of an axial fan in its axial direction.

SUMMARY OF THE INVENTION

In view of prevailing demands for inexpensive heat exchangers for smallhousings, the above problems should be solved with a heat exchanger witha simple structure by minimizing the number of additional parts, the useof expensive parts, and the increase in assembly cost. With theforegoing circumstances in mind, an object of the present invention isto provide an inexpensive heat exchanger that is installable in a smallhousing and capable of achieving both a high heat exchange efficiencyand a high flow rate of inside air.

A heat exchanger for cooling the interior of a housing according to thepresent invention includes a heat exchanger case mounted on a wall of ahousing containing heat generating parts, the heat exchanger case havingan inside air inlet through which an air flows into the housing and aninside air outlet through which an air flows back to the housing formedtherein, a single heat exchanger heat sink including a firstpartitioning member for separating the inside of the heat exchanger caseinto an inside air passage through which the air from inside the housingflows and an outside air passage through which the air from outside thehousing flows, inner fins provided on a surface of the firstpartitioning member facing the inside air passage, and outer finsprovided on a surface of the first partitioning member facing theoutside air passage, an inside air fan for forcing the air inside thehousing to flow in the inside air passage having the inner fins providedtherein through the inside air inlet and discharging the air flowing inthe inside air passage through the inside air outlet, and an outside airfan for forcing the air outside the housing to flow in the outside airpassage having the outer fins provided therein through an outside airinlet formed in the housing and discharging the air flowing in theoutside air passage through an outside air outlet formed in the housing.In this heat exchanger, the first partitioning member, inner fins andouter fins, which form the heat exchanger heat sink, respectively extendin the same longitudinal direction. The inside air outlets include atleast one first inside air outlet formed in the heat exchanger case at aportion near one longitudinal end of the heat exchanger heat sink, andat least one second inside air outlet formed in the heat exchanger caseat a portion near another longitudinal end of the heat exchanger heatsink. The inside air inlet is formed in the heat exchanger case betweenthe first inside air outlet and the second inside air outlet. The insideair fan is an axial fan disposed facing front edges of the inner fins.The inside air fan forces the air inside the housing to flow in theinside air passage through the inside air inlet and discharge the airflowing through the inside air passage through both of the first insideair outlet and the second inside air outlet.

The inside air inlet and the inside air fan may be installed at aposition where the temperature of the air discharged from the firstinside air outlet and the temperature of the air discharged from thesecond inside air outlet become substantially equal to each other.

The heat exchanger case may be a substantially rectangularparallelepiped structure made of a sheet metal, equipped with a flangefor attaching the structure to a wall of the housing and having thefirst inside air outlet and the second inside air outlet formed therein.

The heat exchanger heat sink may be an aluminum or aluminum alloy moldedproduct manufactured by extrusion from a die and cut to a specificdimension in the longitudinal direction without any other cuttingprocess.

A first filling member may be installed between front edges of the innerfins and an inner surface of the heat exchanger case between the insideair inlet and the first inside air outlet, and a second filling membermay be installed between the front edges of the inner fins and an innersurface of the heat exchanger case between the inside air inlet and thesecond inside air outlet.

A second partitioning member having no fins formed on the surfacethereof and having substantially the same width as the firstpartitioning member may be connected to one or both longitudinal ends ofthe first partitioning member forming the heat exchanger heat sink toseparate the one or both longitudinal ends of the heat exchanger heatsink from the heat exchanger case.

The present invention can provide an inexpensive heat exchanger that isinstallable in a small housing and capable of achieving both a high heatexchange efficiency and a high flow rate of inside air.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbe apparent from the following description of embodiments with referenceto the appended drawings, in which:

FIG. 1 is a perspective view of a heat exchanger for cooling theinterior of a housing according to the first embodiment of the presentinvention;

FIG. 2 is a schematic sectional view showing the structure of the heatexchanger in FIG. 1;

FIG. 3 is a perspective view of a heat exchanger heat sink used in theheat exchanger in FIG. 1;

FIG. 4 is a perspective view of corrugated fins used in the heatexchanger in FIG. 1;

FIG. 5 is a perspective view of a first variation of the heat exchangerin FIG. 1, with a heat exchanger case having a different structure fromthat in FIG. 1;

FIG. 6 is a schematic sectional view showing the structure of the heatexchanger in FIG. 5;

FIG. 7 is a schematic sectional view showing a second variation of theheat exchanger in FIG. 1, with an outside air fan and outside airoutlets mounted at different positions from those in FIG. 1;

FIG. 8 is a schematic sectional view showing the structure of a heatexchanger for cooling the interior of a housing according to the secondembodiment of the present invention;

FIG. 9 is a schematic sectional view showing the structure of a heatexchanger for cooling the interior of a housing according to the thirdembodiment of the present invention;

FIG. 10A is a schematic sectional view showing the structure of a heatexchanger for cooling the interior of a housing according to the fourthembodiment of the present invention;

FIG. 10B shows the heat exchanger in FIG. 10A, wherein the panel havingan outside air fan attached thereto is removed from the housingcontaining heat generating parts;

FIG. 11A is a schematic sectional view showing the structure of a heatexchanger for cooling the interior of a housing according to the fifthembodiment of the present invention;

FIG. 11B is an external view, as viewed from an inside air fan mountingsurface, of the heat exchanger case of the heat exchanger in FIG. 11Afrom which an inside air fan is removed;

FIG. 12 is a schematic sectional view showing the structure of a heatexchanger for cooling the interior of a housing according to the sixthembodiment of the present invention;

FIG. 13 is a graph schematically showing the pressure-flow ratecharacteristics (P-Q characteristics) of the axial fan and centrifugalfan;

FIG. 14 is a schematic sectional view of a first example of structure ofa prior art heat exchanger for cooling the interior of a housing; and

FIG. 15 is a schematic sectional view of a second example of structureof a prior art heat exchanger for cooling the interior of a housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A heat exchanger for cooling the interior of a housing according to thefirst embodiment of the present invention will now be described withreference to FIGS. 1-4.

As shown in FIG. 2, an air inside a housing 2 containing hermeticallyheat generating parts such as electronic parts and electric wiring partsis forced by an inside air fan 5, which is attached to an outer surfaceof a heat exchanger case 3 and connected to an inside air inlet 7 and isarranged to face front edges 15 of inner fins 14 (see FIG. 3), to flowin the heat exchanger case 3 through an inside air inlet 7 formedtherein and flow into an inside air passage 19. In the inside airpassage 19, the air flows partially upward and partially downward,losing heat as it flows between the inner fins 14 installed in theinside air passage 19, and is discharged through the first, or upper,inside air outlet 8 and second, or lower, inside air outlet 9.

The temperature of the air drops because its heat is removed by theinner fins 14. The low temperature air discharged through the first andsecond inside air outlets 8, 9 flows over the surfaces of the heatgenerating parts (not shown), taking heat from them and decreasing theirtemperature. The air inside the heat-generating-part containing housing2, which circulates within the housing 2 and takes heat from the heatgenerating parts so that temperature of the air is raised, is forcedagain by the inside air fan 5 back to the heat exchanger 1.

To keep low the temperature of the heat generating parts, it is requiredthat the difference between the temperature of the heat generating partsand the air temperature inside the housing 2 should be large and that alarge volume of air should flow through the first and second inside airoutlets 8, 9 and flow over the surfaces of the heat generating parts athigh velocity.

In this embodiment, as shown in FIG. 2, the first inside air outlet 8 isformed in the upper section of the inside air passage 19, the secondinside air outlet 9 is formed in the lower section of the inside airpassage 19, and the inside air fan 5 and inside air inlet 7 are locatedbetween the first inside air outlet 8 and the second inside air outlet9. The heat exchanger heat sink 12 can therefore use long andfine-pitched (i.e., a large number of) fins 14, 16 having a largesurface area, as shown in FIG. 3. The fins with a large surface areaprovide a high heat exchange efficiency.

Since the distance from the inside air inlet 7 to the first and secondinside air outlets 8, 9 is shortened and the cross section of the insideair passage 19 through which the air flows upward and downward isenlarged, the pressure drop of the air flow in the inside air passage 19from the inside air inlet 7 to the first and second inside air outlets8, 9 is reduced and accordingly a large volume of air can be dischargedthrough the first and second inside air outlets 8, 9.

With the inside air fan 5 and inside air inlet 7 located at a positionwhere the temperature of the air discharged through the first inside airoutlet 8 and the temperature of the air discharged through the secondinside air outlet 9 become substantially equal to each other, it ispossible to avoid a circumstance where an air of insufficient heatdissipation, maintaining high heat, is caused to flow back to theheat-generating-part containing housing 2 through either the firstinside air outlet 8 or the second inside air outlet 9. The phenomenonthat an air of insufficient heat dissipation, maintaining high heat, iscaused to flow back to the heat-generating-part containing housing 2through only one of the first inside air outlet 8 and the second insideair outlet 9 indicates that the inner fins 14 are only partially usedand therefore the heat exchange efficiency is lowered.

The heat exchanger case 3 is a substantially rectangular parallelepipedstructure equipped with a flange 4 (see FIG. 5) for attaching the heatexchanger case 3 to an inner wall of the heat-generating-part containinghousing 2, as well as openings for the inside air inlet 7 and inside airoutlets 8, 9. The heat exchanger case 3 with such a structure can beeasily made at low cost by sheet metal working.

The heat exchanger heat sink 12 shown in FIG. 3 is an aluminum oraluminum alloy product molded by extrusion using a die and has identicalcross sections at any level in the longitudinal (height) direction. Theheat exchanger heat sink 12 can be manufactured at low cost by simplycutting the molded product extruded from the die to a predeterminedlength without any other cutting process. This heat exchanger heat sink12 can be manufactured at the lowest cost if it can be manufactured onlyby cutting the aluminum or aluminum alloy product molded by extrusionfrom a die to a predetermined length. The parts cost and assembly costrequired for the heat exchanger heat sink 12 can be reduced by using asingle heat exchanger heat sink 12 for the plurality of inside airoutlets 8, 9.

Since the heat exchanger case 3 is a simple rectangular parallelepipedstructure that can be manufactured easily only by cutting, bending, andbonding a sheet metal, without any machining or molding process thatwould increase the manufacturing cost or the thickness of the heatexchanger case 3 and make its downsizing difficult, a thin andlightweight heat exchanger case 3 can be obtained at low cost.

Increasing the width of the heat exchanger heat sink 12 or the height ofthe fins in order to increase the surface area of the fins wouldgenerally require a large and expensive extrusion die. In thisembodiment, as can be seen from the shape of the heat exchanger heatsink 12 shown in FIG. 3, since the first partitioning member 13, innerfins 14, and outer fins 16 have their longitudinal directions (heightdirection in FIG. 3) coincident with the direction of extrusion from theextrusion die, the surface area of the fins can be increased byincreasing the length (height) of the heat exchanger heat sink 12without the need to enlarge the extrusion die. When such a heatexchanger heat sink 12 having its height (longitudinal dimension) largerthan its width (lateral dimension) is used, the structure having theinside air inlet 7 disposed between the first inside air outlet 8 andsecond inside air outlet 9 is particularly effective to increase theflow rate of the inside air. In this first embodiment, corrugated fins18 shown in FIG. 4 may be used instead of the heat exchanger heat sink12 shown in FIG. 3 formed of the first partitioning member 13, innerfins 14, and outer fins 16.

In the example shown in FIG. 2, the first and second inside air outlets8, 9 disposed in the upper and lower sections of the inside air passage19 are formed in the side of the heat exchanger case 3 to which theinside air fan 5 is attached. Alternatively, at least one of the firstand second inside air outlets 8, 9 disposed in the upper and lowersections of the inside air passage 19 may be formed in a side of theheat exchanger case 3 that is perpendicular to the side to which theinside air fan 5 is attached, as shown in FIGS. 5 and 6. FIG. 5 shows anexample in which the first inside air outlet 8 is formed in the top ofthe heat exchanger case 3, while FIG. 6 shows an example in which thefirst and second inside air outlets 8, 9 are formed in the top andbottom of the heat exchanger case 3.

The first and second inside air outlets 8, 9 formed in the top and/orbottom of the heat exchanger case 3 as shown in FIG. 5 or 6 prevent airaccumulation spots from being created in the first corners 25, 25 (seeFIG. 2) formed by the first partitioning member 13 and inner fins 14forming the heat exchanger heat sink 12 and the heat exchanger case 3,so the air can flow smoothly between the inner fins 14 to bothlongitudinal ends of the heat exchanger heat sink 12. This enables thesurfaces of the inner fins 14 to be efficiently utilized for heatexchange and can provide a high heat exchange efficiency. In case wherethe first and second inside air outlets 8, 9 formed in the top andbottom of the heat exchanger case 3, the low temperature air dischargedthrough the first and second inside air outlets 8, 9 may sometimesbecome difficult to flow easily toward the heat generating parts, butsuch a problem may be solved by attaching a deflection plate 27 to atleast one of the first and second inside air outlets 8, 9 to deflect theair flow discharged therethrough as shown in FIG. 6.

Furthermore, to suppress the temperature rise of the heat generatingparts that generate a particularly large amount of heat, deflectionplates (not shown) may be attached to the first and second inside airoutlets 8, 9 to selectively direct the air from the outlets 8, 9 towardthose heat generating parts.

On the other hand, the air outside the heat-generating-part containinghousing 2 is forced by the outside air fan (axial fan) 6 disposed facingfront edges 17 of the outer fins 16 to flow in the housing 2 through theoutside air inlet 10 formed in the wall of the housing 2. After passingthrough the outside air fan 6, the air flows into the outside airpassage 20, takes heat from the outer fins 16 installed in the outsideair passage 20 as it flows between the outer fins 16, and is dischargedthrough the outside air outlet 11. In this embodiment, a baffle plate 28(see FIG. 2) is provided to prevent the air outside theheat-generating-part containing housing 2 forced by the outside air fan6 to flow in the outside air passage 20 through the outside air inlet 10from exiting through the outside air outlet 11 without flowing betweenthe outer fins 16.

In this embodiment, the outside air fan 6 is located near the lower endof the heat exchanger heat sink 12 and the outside air outlet 11 isformed in the housing 2 at a portion near the upper end of the heatexchanger heat sink 12, as shown in FIG. 2. Alternatively, the outsideair fan 6 may be located near the upper end of the heat exchanger heatsink 12 and the outside air outlet 11 may be formed in the housing 2 ata portion near the lower end of the heat exchanger heat sink 12.Alternatively, the outside air fan 6 may be located near the middle inthe longitudinal direction of the heat exchanger heat sink 12 and one ofthe outside air outlets may be formed in the housing 2 at a portion nearthe lower end of the heat exchanger heat sink 12 and the other one ofthe outside air outlets may be formed in the housing 2 at a portion nearthe upper end of the heat exchanger heat sink 12, as shown in FIG. 7.

In this embodiment, the heat exchanger heat sink 12 is verticallyoriented in the heat exchanger case 3 with the first inside air outlet 8and second inside air outlet 9 being located near the upper and lowerends, respectively, of the heat exchanger heat sink 12 as shown in FIGS.2 and 3. Alternatively, the heat exchanger heat sink 12 may behorizontally oriented in the heat exchanger case 3 with the first insideair outlet 8 and second inside air outlet 9 being located near the leftand right ends, respectively, of the heat exchanger heat sink 12.

For safety reasons, a fan guard may be provided outside the outside airfan 6 and the outside air outlet 11 may have punched slits to preventthe entrance of foreign matters.

As described above, the heat exchanger according to the first embodimentof the present invention is the same as those of the prior art in thatit employs a single heat exchanger heat sink longitudinally extending inthe air flow direction and an axial fan advantageous in obtaining alarge air flow rate so as to force the air to flow from one end of theheat exchanger heat sink to the other end thereof.

In the heat exchanger according to this embodiment, however, thedistance through which the air flows between the inner fins 14 from theinside air inlet 7 to the first and second inside air outlets 8, 9 isapproximately one half the distance of the prior art described above andthe cross-sectional area of the inside air passage 19 through which theair flows between the inner fins 14 is approximately double that of theprior art. In this embodiment, accordingly, even if the inner fins 14has the same surface area and the same heat exchange capacity as thoseof the prior art, the pressure drop of the air flow caused by the innerfins 14 is significantly reduced and the flow rate of the air dischargedthrough the first inside air outlet 8 and second inside air outlet 9 issignificantly increased according to the P-Q characteristics of theinside air fan 5, so that the temperature of the air inside the housingas well as the temperature of the heat generating parts can be kept lowwithout using a stirring fan.

Furthermore, according to this embodiment, since the pressure drop ofthe air flow caused by the inner fins 14 is reduced as described above,fine-pitched inner fins 14 causing a high pressure drop can be used.Consequently, since the volume of the heat exchanger heat sink 12 can bereduced while the surface area of the inner fins 14 can be kept to thesame degree, the entire size of the heat exchanger can be reduced. Thearrangement of this embodiment is also applicable to aheat-generating-part containing housing 2 of small size. This embodimentis also advantageous in downsizing the entire size of the heatexchanger, because the pressure drop is reduced as described above and anecessary air flow rate can be obtained with a relatively small fan.

The inside air inlet 7 and inside air fan 5 are installed at a positionwhere the amount of heat dissipation per unit flow rate of the insideair from the inside air inlet 7 to the first inside air outlet 8 and theamount of heat dissipation per unit flow rate of the inside air from theinside air inlet 7 to the second inside air outlet 9 becomesubstantially equal to each other. With this, the temperature of the airdischarged from the first inside air outlet 8 and the temperature of theair discharged from the second inside air outlet 9 become substantiallyequal to each other. Consequently, according to this embodiment, it ispossible to avoid the reduction of heat exchange efficiency due topartial use of the inner fins as in the case where an air ofinsufficient heat dissipation, maintaining high temperature, is causedto flow back to the heat-generating-part containing housing 2 throughonly one inside air outlet and thus a high heat exchange efficiency canbe achieved.

From the structural viewpoint, the heat exchanger according to thisembodiment only differs from the prior art heat exchanger (illustratedin FIG. 14) in the positions of the inside air inlet and inside air fanand the number of openings for the inside air outlets formed in the heatexchanger case. This means that the heat exchanger according to thisembodiment can be manufactured at low cost because there are noadditional parts, no replacement with expensive parts, no additionalassembling steps, and little factors that increase the cost, as comparedwith the prior art heat exchanger.

The structure of the heat exchanger shown in FIG. 2 may be modified byattaching both the inside air fan 5 and the outside air fan 6 such thatthe air is sent in the directions opposite to the directions shown inFIG. 2, replacing accordingly the first and second inside air outlets 8,9 with the first and second inside air inlets, replacing the inside airinlet 7 and outside air inlet 10 with the inside air outlet and outsideair outlet, and replacing the outside air outlet 11 with the outside airinlet.

In this modified structure of the heat exchanger, when an axial fan isused as the inside air fan (and as the outside air fan), the flow rateis not affected much by obstacles (fins in the case of the example inFIG. 2) located on the outlet side, but is significantly reduced bythose located on the inlet side, deviating from the P-Q characteristics.The reduction in flow rate of the inside air is against the object ofthe present invention and the reduction in flow rate of the outside airis also undesirable. On the other hand, increasing the distance betweenthe intake side of the fan and the obstacles to the extent that the flowrate is not affected would unavoidably result in a larger heatexchanger. Although the structure of the heat exchanger according to thefirst embodiment (FIG. 2) could be modified as described above, theresultant structure would not be desirable to achieve the object of thepresent invention.

Second Embodiment

A heat exchanger for cooling the interior of a housing according to thesecond embodiment of the present invention will now be described withreference to FIG. 8.

In the first embodiment described above, the outside air fan 6 ismounted inside the housing 2 containing heat generating parts as shownin FIG. 2. In the second embodiment, the outside air fan 6 is mountedoutside the housing 2. With this arrangement, the outside air fan 6protrudes out of the housing 2.

In the heat exchanger according to this embodiment, if there are norestrictions in aesthetic terms or in terms of the installation locationof the housing 2, no baffle plate 28 (see FIG. 6) is required to preventthe air outside the housing 2 forced by the outside air fan 6 to flow inthe outside air passage 20 through the outside air inlet 10 from exitingthrough the outside air outlet 11 without passing through the outer fins16. Accordingly, in this embodiment, since the space occupied by thebaffle plate 28 is not required, the size (in this case, the thickness(i.e., depth)) of the heat exchanger 1 can be reduced, in addition tothe reduction in the number of parts, parts cost, and assembly cost.

Third Embodiment

A heat exchanger for cooling the interior of a housing according to thethird embodiment of the present invention will now be described withreference to FIG. 9.

In the first embodiment described above, the outside air fan 6 isdisposed facing the front edges of the outer fins 16, as shown in FIG.2.

On the other hand, in the third embodiment, the outside air fan 6 isinstalled in a space extended in the longitudinal direction from theheat exchanger heat sink 12 (right above the heat exchanger heat sink 12in FIG. 9) and a third partitioning member 24 is connected to the firstpartitioning member 13 forming the heat exchanger heat sink 12. Withthis arrangement, the air forced by the outside air fan 6 to flow in theoutside air passage 20 from outside the housing 2 through the outsideair inlet 10 flows between the outer fins 16 forming the heat exchangerheat sink 12 without being mixed with the air coming from inside thehousing 2 and is discharged through the outside air outlet 11.

In the heat exchanger according to this embodiment, the verticaldimension (height) of the heat exchanger 1 is increased, but itsthickness (depth) can be reduced, although the outside air fan 6 doesnot protrude out of the housing 2 in its depth direction. Consequently,the heat exchanger according to this embodiment is applicable to smallhousings that have enough height but not enough depth.

Fourth Embodiment

A heat exchanger for cooling the interior of a housing according tofourth embodiment of the present invention will now described withreference to FIGS. 10A and 10B.

In the first embodiment described above, the outside air inlet 10 andoutside air outlet 11 are formed in the wall of the heat-generating-partcontaining housing 2 and the outside air fan 6 is mounted on the innerwall of the housing 2 so as to be connected to the outside air inlet 10,as shown in FIG. 2. On the other hand, in the fourth embodiment, anopening larger than the outside air inlet 10 and outside air outlet 11is formed in the wall of the heat-generating-part containing housing 2and is covered by a panel 29 mounted outside the housing 2. This panel29 has an outside air inlet 10 and an outside air outlet 11 formed asshown in FIG. 10B. The outside air fan 6 is mounted on the side of thepanel 29 facing the housing 2 so as to be connected to the outside airinlet 10.

By removing the panel 29 thus arranged from the outside of the housing2, the outer fins 16 can be exposed easily. The heat exchanger accordingto this embodiment, therefore, facilitates the cleaning of the outerfins 16 contaminated or clogged by dusts, cutting fluid, etc., suckedfrom outside the housing 2, as well as the cleaning, replacement, orother maintenance of the outside air fan 6 without the need to open thedoor of the housing 2 and thus also prevents the interior of theheat-generating-part containing housing 2 from being contaminated byopening the door.

Fifth Embodiment

A heat exchanger for cooling the interior of a housing according to thefifth embodiment of the present invention will now described withreference to FIGS. 11A and 11B.

In the first embodiment described above, the gap between the inside airfan 5 and the front edges of the inner fins 14 is limited to thethickness of a thin metal plate forming the heat exchanger case 3 asshown in FIG. 2. On the other hand, in the fifth embodiment, as shown inFIG. 11A, a first filling member 21 is installed between the front edges15 of the inner fins 14 and the inner surface of the heat exchanger case3 between the inside air inlet 7 and the first inside air outlet 8, anda second filling member 22 is installed between the front edges 15 ofthe inner fins 14 and the inner surface of the heat exchanger case 3between the inside air inlet 7 and the second inside air outlet 9. Thefirst filling member 21 and the second filling member 22 have the samethickness.

By installing the first filling member 21 and second filling member 22,a gap is formed between the front edges of the inner fins 14 and theinner surface of the heat exchanger case 3 adjacent to the inside airfan 5. With this arrangement, as shown in FIG. 11B, even if the width ofthe heat exchanger heat sink 12 is larger than the diameter of theinside air fan 5, the air drawn in by the inside air fan 5 reliablyflows between the inner fins of the heat exchanger heat sink 12extending around the inside air fan 5, so a small-sized inside air fan 5having a small diameter can be incorporated into the heat exchanger 1.Preferably, the first and second filling members 21, 22 have a thicknessin the range of several millimeters to a dozen or so millimeters.Increasing the thickness thereof more than necessary is meaningless andwould inhibit downsizing of the heat exchanger 1.

Sixth Embodiment

A heat exchanger for cooling the interior of a housing according to thesixth embodiment of the present invention will now be described withreference to FIG. 12.

In the first embodiment described above, the longitudinal (upper andlower) ends of the heat exchanger heat sink 12 are in contact with theheat exchanger case 3 as shown in FIG. 2. On the other hand, in thesixth embodiment, second partitioning members 23, 23 havingsubstantially the same width as the first partitioning member 13 andhaving no fins on the surface thereof are connected to the longitudinal(upper and lower) ends of the first partitioning member 13 forming theheat exchanger heat sink 12 to separate the longitudinal ends of theheat exchanger heat sink 12 from the heat exchanger case 3. The secondpartitioning member 23 may be attached to only one end (e.g., only upperend) of the first partitioning member 13 of the heat exchanger heat sink12 for dimensional reasons.

The second partitioning members 23 thus arranged prevent airaccumulation spots from being created in the first corner 25 formed bythe first partitioning member 13 and inner fins 14 forming the heatexchanger heat sink 12 and the heat exchanger case 3 and in the secondcorner 26 formed by the first partitioning member 13, outer fins 16, andheat exchanger case 3. As described above, according to this embodiment,although the second partitioning members 23 slightly increase the costof the heat exchanger 1, they enhance the heat exchange efficiency byhelping the air pass smoothly between the inner fins 14 or outer fins 16to the upper and lower ends of the heat exchanger heat sink 12 and thusthe surfaces of the inner fins 14 and/or outer fins 16 forming the heatexchanger heat sink 12 be used efficiently.

Instead of connecting the second partitioning members 23, 23 to theupper and lower ends of the first partitioning member 13 forming theheat exchanger heat sink 12, the upper and lower sections of the innerfins 14 and/or outer fins 16 forming the heat exchanger heat sink 12 maybe partially removed by cutting to separate the longitudinal ends of theheat exchanger heat sink 12 from the heat exchanger case 3.

Adding the cutting process for removing partially the inner fins 14and/or outer fins 16 of the heat exchanger heat sink 12 molded byextrusion is not desirable, however, because it significantly increasesthe manufacturing cost of the heat exchanger.

The first and second inside air outlets 8, 9 formed in the top andbottom, instead of being formed in the side wall, of the heat exchangercase 3 as in FIG. 5 or 6 can prevent the air accumulation spots frombeing created, but make it difficult to direct the cool air dischargedthrough the first and second inside air outlets 8, 9 toward the heatgenerating parts. In addition, the outside air outlet 11 cannot beformed in the top or bottom of the heat exchanger case 3; it can beformed only in the side wall of the housing 2.

Preferably, the gap between the longitudinal ends of the heat exchangerheat sink 12 and the inner surface of the heat exchanger case 3 is in arange of several millimeters to dozen or so millimeters, because anunnecessarily wide gap between the longitudinal ends of the heatexchanger heat sink 12 and the inner surface of the heat exchanger case3 could not noticeably increase the heat exchange efficiency.

As described above, according to the present invention, an inexpensive,small-sized heat exchanger 1 can be implemented that is capable ofachieving both a high heat exchange efficiency and a high flow rate ofinside air and is applicable to a small housing containing parts thatgenerate a large amount of heat. It should be appreciated that the heatexchange efficiency as used herein is a value obtained by dividing thedifference between the amount of heat generated inside the housing 2 andthe amount of heat dissipated from the surface of the housing 2 by thedifference (ΔT (K)) between the air temperature inside the housing 2 andthe air temperature outside the housing 2. The amount of heat dissipatedfrom the surface of the housing 2 is a function of ΔT (=the airtemperature inside the housing 2 minus the air temperature outside thehousing 2) and increases substantially linearly as ΔT increases.

1. A heat exchanger for cooling the interior of a housing comprising: aheat exchanger case mounted on a wall of a housing containing heatgenerating parts, the heat exchanger case having an inside air inletthrough which an air flows into the housing and an inside air outletthrough which an air flows back to the housing formed therein; a singleheat exchanger heat sink including a first partitioning member forseparating the inside of the heat exchanger case into an inside airpassage through which the air from inside the housing flows and anoutside air passage through which the air from outside the housingflows, inner fins provided on a surface of the first partitioning memberfacing the inside air passage, and outer fins provided on a surface ofthe first partitioning member facing the outside air passage; an insideair fan for forcing the air inside the housing to flow in the inside airpassage having the inner fins provided therein through the inside airinlet and discharging the air flowing in the inside air passage throughthe inside air outlet; and an outside air fan for forcing the airoutside the housing to flow in the outside air passage having the outerfins provided therein through an outside air inlet formed in the housingand discharging the air flowing in the outside air passage through anoutside air outlet formed in the housing; wherein the first partitioningmember, inner fins and outer fins, which form the heat exchanger heatsink, respectively extend in the same longitudinal direction; the insideair outlets include at least one first inside air outlet formed in theheat exchanger case at a portion near one longitudinal end of the heatexchanger heat sink, and at least one second inside air outlet formed inthe heat exchanger case at a portion near another longitudinal end ofthe heat exchanger heat sink; the inside air inlet is formed in the heatexchanger case between the first inside air outlet and the second insideair outlet; the inside air fan is an axial fan disposed facing frontedges of the inner fins; the inside air fan forces the air inside thehousing to flow in the inside air passage through the inside air inletand discharge the air flowing through the inside air passage throughboth of the first inside air outlet and the second inside air outlet. 2.The heat exchanger according to claim 1, wherein the inside air inletand the inside air fan are installed at a position where the temperatureof the air discharged from the first inside air outlet and thetemperature of the air discharged from the second inside air outletbecome substantially equal to each other.
 3. The heat exchangeraccording to claim 1, wherein the heat exchanger case is a substantiallyrectangular parallelepiped structure made of a sheet metal, equippedwith a flange for attaching the structure to a wall of the housing andhaving the first inside air outlet and the second inside air outletformed therein.
 4. The heat exchanger according to claim 1, wherein theheat exchanger heat sink is an aluminum or aluminum alloy molded productmanufactured by extrusion from a die and cut to a specific dimension inthe longitudinal direction without any other cutting process.
 5. Theheat exchanger according to claim 1, wherein a first filling member isinstalled between front edges of the inner fins and an inner surface ofthe heat exchanger case between the inside air inlet and the firstinside air outlet, and a second filling member is installed between thefront edges of the inner fins and an inner surface of the heat exchangercase between the inside air inlet and the second inside air outlet. 6.The heat exchanger according to claim 1, wherein a second partitioningmember having no fins formed on the surface thereof and havingsubstantially the same width as the first partitioning member isconnected to one or both longitudinal ends of the first partitioningmember forming the heat exchanger heat sink to separate the one or bothlongitudinal ends of the heat exchanger heat sink from the heatexchanger case.